Vacuum tube circuit for operating relays



Sept- 30, 1947- V M. G. NlcHoLsoN, JR 2,428,125

VCUU TUBE .JIRCUIT FOR OPERATING RELAYS Fned'Apl-il 19, 1944 Gttcnui;

Patented 'Sept 30, 1947.

Madison G. Nicholson, Snyder, N. Y., assigner to Colonial Radio Corporation, Buffalo, N. Y.

,application april 19, 1944, ser-nu No. 5.21.80:

(ci. 11s-32o) Claims.

This invention relates to a new and improved circuit for operating relays, and more particularly, circuits of the kind wherein the plate current of a vacuum tube, flowing through a solenoid, mechanically opens or closes one or more relay contacts.

In electrical work, there are many occasions where it is desired' to utilize a control voltage to cause the operation of a relay. As a typical example of the problem to which my invention is addressed, assume that a control voltage is applied between the grid and cathode of a threeelement vacuum tube in such a manner as to make the grid negative with respect to the cathode.- Connected in the plate circuit of such a tube there may be the operating winding of a relay which is to open when the control voltage equals -50 volts. Assume also that the only tube available is o ne in which the plate current reaches a 'value at which the relay opens when the grid voltage is -10 volts with respect to the cathode.

It will be clear that if the control voltage is applied directly to the grid and cathode of the tube, the relay will not operate properly, but will open when the control voltage equals -10 volts, whereas it should stay closed until the control voltage equals -50 volts. This premature operation of the relay will cause malfunctioning of the circuits depending upon it. In the past, under quired to move the relay from open toclosed position than to hold it in closed position.

Greatly improved operation may be obtained ii the tube can be made to operate more like an on-oii switch; that is to say, in the example given, an improvement in operation would be obtained if the plate current stayed at maximum while the control voltage moved from 0 to 40, and thereafter dropped toward cutoil as the control voltage moved from -40 to 50. This improvement is possible using thecircuits oi this invention.

Among the objects of my invention are the following: n

To provide a relay circuit whose operating characteristics are less susceptible to variations resulting from change in tube characteristics.

To provide a circuit which will effectively alter the operating characteristics of any particular which an available vacuum such conditions, it has been customary to provide a-voltage divider between the control voltage source and the cathode and control grid of the tube.

have the relay open at -50 volts, a 5 to i voltage divider would be employed to reduce the control voltage; that is, the cathode and control electrode` would be connected across l/s of the total resisti' ance of the voltage divider.

` plate current might be suillciently reduced so that a slightjar would knock therelay open and the plate current would not be sufllciently strong to close it, because somewhat more current is re- In the example above given, if it is desired to.

vacuum tube to make it fit the control voltages desired to be employed.

To provide a circuit of the class described in tube may be arranged 'to operate efficiently with control voltages which would otherwise not be adapted for use with the tube.

To provide a circuit oi the class described in which the opening and closing of the relay is made more definite and certain.

To provide a circuit of the class described in which the operation of the relay may be made more deiinite from the standpoint of time and also with respect to control-voltage.

Still other objects and advantages of my invention will be apparent from the specification.

In this application I have particularly pointed out and distinctly claimed the part, improvement, or combination which I claim as my invention or discovery, and I have explained the principles thereof and the best mode in which I have contemplated applying those principles so as to distinguish my invention from other inventions.

In the drawing,

Fig. 1 is a circuit diagram of one form of cirvrcuit in accordance with my invention,

Fig, 2 is asimilar view of a modified form, and

. like characters represent 3 sistor Il. The plate circuit may comprise the winding I3 of relay Il, resistor II, and may be completed through the usual B source.

In this figure, a. 5 to 1 improvement in relay operation in terms of variation of characteristics ofthe tube and relay may be obtained by employing battery I0, so poled as to make the control electrode I2g positive with respect to the cathode, and having a voltage of 40 volts. Resistance Il is preferably of a substantial value; for example, one megohm, so as to effectively limit grid current. Under these conditions it will be clear that the grid will remain positive at al1 times and the tube will be drawing its maximum current until the control voltage is more negative than -40 volts.

'I'he platecurrent will remain constant until the control voltage passes beyond -40 volts in the negative direction, whereupon it will begin to decrease and the relay will open at -50 volts, at which time the grid will be at -10 volts; that is to say, the tube varies the relay current only i-n the last 10 volts of change of the control voltage, and a jar which in the former instance would have opened the relay and causedmalfunctioning of the relay controlled circuits will not now affect the relay over the range from to 40 volts.

Under certain conditions it employ biasing batteries, and ticularly true i-n case the plate from a power pack. Under such circumstances the circuit of Fig. 2 may be employed, wherein the same elements as in Fig. 1, but in this instance I may employ a resistor l5 in' series with a B battery supply and a relay winding, and may provide a connection from the B supply through additional resistor I6 to the control grid |29.

In this example, it is desired that the voltage drop through resistor Il be the vsame as before; i. e., -40 volts; and, therefore, the B supply current flowing through resistance II should be .04 milliampere. The resistance of Il plus i6 will, therefore, be so related to plate voltage as to give this current according to the well-known formula E=IR.

If the plate supply voltage is 400 volts, the control voltage 50 volts, and Il one megohm, then resistance I6 will be 10.25 megohms, this producing the required voltage drop of 40 volts in Il. The action of the circuit may be more clearly understood with reference to Fig. 3, in which curve A represents the characteristics of the tube in terms of plate current plotted against control voltage.

If the control voltage were applied directly to the grid from 0 to -50 volts, it would be apparent that after it has reached 10 volts, the relay has opened and nothing happens for any further increase in control voltage in the negative direction, as shown by curve A. Curve B shown may represent plate current of the tube for varying control voltage when the control voltage is applied to the tube through a 5 to 1 voltage divider, and it will be observed that plate current now decreases from its maximum for any negative control voltage and that. very substantial decreases in plate current occur for drops in control voltage which are not desired to open the relay.

Curves C and D may represent the operation of the circuit shown in Figs. 1 and 2 for different values of bucking voltage from battery I0 or resistor Il, and'it will be observed that by appropriate choicevin value of this bucking voltage, operation of the tube (drop from maximum is undesirable to this may be parsupply is obtained' 4 current to opening) may be made to occur within any 10 volts variation in control voltage. Curves B and C are drawn to scale .for the same operating voltage; i. e., 50 volts, and C represents the improvement which my invention anords.

While for purposes of clarity of disclosure I have used the example of 50 volts control voltage and 10 volts operating voltage on the grid of the tube, it should be understood that this is only by way of example, and that the same principles may .be applied for diierent values of control voltage and operating voltage.

'I'he circuit of Fig. 1 has the characteristic that the required operating voltage to open or close the relay is for all practical purposes independent of the plate supply voltage over a wide range o! plate voltage, as indicated in Fig. 4. Thus, this circuit is of particular value in cases where it is desired that the operating point be practically constant with a wide range ot plate sumly voltage.

On the other hand, the circuit in Fig. 2 has the characteristic that the required operating or control voltage to open or close the relay is approximately proportional to the plate supply voltage, as will be seen from Fig. 5. Such a characteristic is useful when it is desired that the operating voltage be proportional to the supply voltage. This is frequently the case where the tube or tubes (not shown) furnishing the control voltage have their plate circuits fed from the same source .that supplies the plate circuit of tube I2.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the spirit and scope of my invention, as will be apparent to those skilled in theart.

I claim:

1. Electrical apparatus, comprising, in combination, a thermionic tube having a cathode, an anode, and a control electrode, and a source of anode-cathode current Supply. a relay having an energizing winding connected in the space current path of said tube, a source of potential difference and a resistor connected in series between said cathode and control electrode with a polarity to impress a positive bias on said control electrode, and means for impressing a control voltage between said cathode and control electrode with a polarity to make said control electrode negative with respect to said cathode, said energizing Winding being normally energized over a substantial portion of the range of variation of the control voltage, the magnitude of the positive biasing voltage being somewhat less than the control voltage for which said relay is to be released, and the magnitude of the positive biasing voltage being so related to the control voltage and to the characteristics of the tube that the range of spurious operation due to vibration and jar is greatly reduced.

2. Electrical apparatus, comprising, in combination, a thermionic tube having a cathode, an anode, and a control electrode, and a source oi anode-cathode current supply, a relay having an energizing winding connected in the space eurrent path of said tube, a source of potential difference and a resistor connected in sexies between said cathode and control electrode with a polarity to impress a positive bias on said control electrode, and means for impressing a control voltage between said cathode and control electrode with a polarity to make said control electrode negative with respect to said cathode, said trol voltage and to the characteristics of energizing winding being normally energized over a substantial portion of the range of variation of the control voltage, the magnitude of the positive biasing voltage being so related to the control voltage for which said relay is to operate that maximum space current ispassed by said tube over a substantial portion of the .range oi variation of the control voltage, the magnitude positive bias being somewhat less than the magnitude of the control voltagefor which the relay of the energizing winding connected in the space current path of said tube, a source of potential diiference and a resistor connected in series between said cathode and control electrode with a polarity toimpress a positive bias on saidcontrol electrode, and means for impressing a control voltage between said cathode and control electrode with a polarity to make said control electrode negative with respect to said cathode, said energizing winding being normally energized over a substantial portion of the range ci.' variation of the control voltage, the magnitude of the positive biasing voltage being somewhat less than the control voltage for which said relay is to be released, said last means comprising a connection including a resistance, from said control electrode to said source oi anode-cathode current supply, and the magnitude of the positive biasing to impress a positive bias on said control electrode, and means for impressing a control voltage between isaid cathode'and control electrode with a polarity to make said tive with respect to said cathode, said energizing winding being normally energized over a substantial portion of the range of variation of the control voltage, the 'magnitude of the positive biasing voltage being somewhat less than the control voltage for which said relaylis to be released, and the value of said resistor being suillciently large as to substantially prevent the flow of grid current, and the magnitude of the positive biasing voltage being so related to the' control 'voltage and to the characteristics of the tube that the range oi spurious operation due to vibration and :lar is greatly reduced,

4. Electrical apparatus, comprising, in cornbination, a thermionic tube having a. cathode, an'

anode and a control electrode, and a source of vanode-cathode current supply, a relay having an energizing winding connected in the space current-path of said tube, a source of potential difference and a resistor connected in series between said cathode and control electrode with a polarity to impress a positive bias on said-control electrode, and means for impressing a control voltage between said cathode and control electrode with a polarity to make said control electrode negative with respect to said cathode, said energizing winding being normally energized over a substantial portion of the range of variation of the control voltage, the magnitude of the positive biasing voltage being so related to the control voltage for which said relay is to operate that maximum space current is passed by said tube over a substantial portion of the range of variation of the control voltage, and the value of said resistor being suiiiciently large as to substantially prevent the flow of grid current, the magnitude of thepositive bias being somewhat less than the magnitude of the control voltage for which the relay is to be released, and the magnitudeof the positive biasing voltage being .so related to the control voltage and to the characteristics of the tube that the range of spurious operation due to vibration and jar -is greatly reduced.

5. Electrical control electrode nega` voltage being so related to the control voltage and to the characteristics of the tube that the range of spurious operation due to vibration and jar'is greatly reduced.

6. Electrical apparatus, comprising, in combination, a thermionic tube having a. cathode, an anode, and a control electrode, and a source of anode-cathode current supply, e,l relay having an energizing winding connected rent path of said tube, a source of potential diiference and a resistor connected in series between said cathode and control electrode with a polarity to impress a positive bias on said control electrode, and means for impressing a control anode-cathode current supply,

' trol voltage and to the voltage between said cathode and control electrode with a polarity trode negative with respect to said cathode, said energizing winding being normally energized over a substantial portion of the range of variation of the control voltage, the magnitude of the biasing voltage being so related to the control voltage for which said relay is to operate that maximum. space current is passed 'by said tube over a substantial portion or the range of variation of the control voltage, said last means comprising a connection including a resistance, from said control electrode to said source of anodecathode current supply, the magnitude of the positive bias being somewhat less than the magnitude of the control voltage for which the relay is to be released, and the magnitude of the positive biasing voltage being so related to the concharacteristics of the tube that the range of spurious operation due to vibration and jar is greatly reduced.

7. Electrical apparatus, comprising, in combination, a thermionic tube having a cathode, an anode, and a control electrode, and a source of a relay having an energizing winding connected in the space current path of said tube, a source of potential difference and a. resistor connected in series between said cathode and control electrode with a polarity tial portionof the range of variation of the conapparatus, comprising, in combination, a thermionic tube having a cathode, an'

trol voltage, the magnitudeof the positive biasing voltage being somewhat less than the control voltage for which said relay is to be released, and the value of said resistor being suiiiclently large as to substantially prevent the flow of grid current, said last means cluding a resistance, from said control electrode in the space curto make said control elecpositive cathode, said energizing comprising a connection inl tube that the range of tween said cathode and control electrode with a l polarity to impress a. positive bias on said control electrode, and means for impressing a control voltage between said cathode and control electrode with a polarity to make said control electrode negative with respect to said cathode, said energizing Winding being normally energized over a substantial portion of the range of variation of the control voltage, the magnitude of the positive i biasing voltage being so related to the control voltage for which said relay is to operate that maximum space current is passed by said tube over a. substantial portion of the range of variation of the control voltage, and the value of said resistor being sufiiciently large as to substantially prevent the ilow of grid current, said last means comprising a connection including a resistance, from said control electrode to said source of anode-cathode current supply, the magnitude of the positive bias being somewhat less than the magnitude of the control voltage for which the relay is to be released, and the magnitude of the positive biasing voltage being so related to the control voltage and to the characteristics of the tube that the range of spurious operation due to vibration and jar is greatly reduced.

9. Electrical apparatus, comprising, in combination, a. thermionic tube having a cathode, an anode, and a control electrode, and a source of anode-cathode current supply, a relay having an energizing winding connected in the space eurrent path of said tube, a source of potential difference and a resistor connected in series between said cathode and control electrode with a polarity to impress a positive bias on said contro1.electrode, and means for impressing a control voltage between said cathode and' control electrode with a polarity to make said control electrode negative with respect to said cathode, said energizing winding being normally energized over a substantial portion oi the range of variation of the control voltage, the magnitude oi' the positive biasing voltage being so related to the control voltage for which said relay is to operate that maximum space current is passed by said tube over a substantial portion of the range of variation of the control voltage, and the value of said resistor being suiiiciently large as to substantially prevent the flow of grid current, said last means comprising a connection including a resistance, from said control electrode to said source of anode-cathode current supply, said thermionic tube and the tube which furnishes the control voltage having a common source ol' space cirrent, the magnitude of the positive bias being somewhat less than the magnitude of the control voltage for which the relay is to be released, and the magnitude of the positive biasing voltage being so related to the contro1 voltage and to the characteristics of the tube that the range of spurious operation due to vibration and Jar is greatly reduced.

10. Electrical apparatus, comprising, in combination, a thermionic tube having a cathode, an anode, and a control electrode, a relay having an energizing winding connected in the space current path of said tube, a source of potential difference and a resistor connected in series between said cathode and control electrode with a polarity to impress a positive bias on said control electrode, and means for impressing a control voltage between said cathode and control electrode with a polarity to make said control electrode negative with respect to said cathode, said energizing winding being normally energized over a substantial portion of the range of variation of the control voltage, the magnitude of the positive biasing voltage being so related to the control voltage being somewhat less than the magnitude of the control voltage i or which the relay is to be released and for which said relay is to operate that maximum space current is passed by said tube over a substantial portion of the range of variation of the control voltage, and the value of said resistor being sufficiently large as to substantially prevent the flow of grid current, said .last means comprising a connection including a resistance, from said control electrode to said source of anode-cathode current supply, a single source of plate current for said thermionic tube and the control tube, whereby the control voltage is substantially proportional to plate voltage, and the magnitude of the positive biasing voltage being so related to the control voltage and to the characteristics of the tube that the range of vspurious operation due to vibration and jar is greatly reduced. 1

MADISON G. NICHOLSON, JR.

. REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,150,440 Hargreaves Mar. 14, 1939 1,738,299 Kille Dec. 3, 1929 2,115,881 Roosenstein May 3, 1938 

